The present invention is directed to an apparatus and method for sequentially removing items from a stack of items, and more particularly concerns an automatic depalletizing system, apparatus, conveyor, machine or method for automatically sequentially removing one or more crates or containers from a vertical stack of crates or containers.
Conventional poultry industry production methods and movement of processed chicken in poultry processing plants involves the placement of processed packaged poultry products in plastic containers or crates at various work stations. These containers or crates are then stacked seven to eight high on a dolly for ease of in-house movement within the poultry processing plant. All the product in the containers on the dollies is cooled to a temperature of about 28.degree. and then moved to a cold storage unit prior to shipment in refrigerated trucks. This cold temperature is maintained during movement from cold storage to the shipping trucks.
Daily shipping orders are placed prior to start-up operations in shipping. The pack-out personnel stage this product next to the pack-out line conveyors in the 28.degree. room using the first-in, first-out method. Each production line requires two pack-out personnel who lift and place each container or crate (weighing between 25 and 125 lbs.) on the conveyor which moves the product down line. Thereafter, approximately three to seven pack-out personnel remove the product from the containers or crates and place it in shipping boxes for transport to the shipping trucks.
This method requires the constant rotation of pack-out personnel lifting the containers on the conveyor with cycle time subject to the stamina variation of the personnel doing the lifting. The heavy lifting combined with the fast-paced nature of the work creates high employee turnover rates. Productivity may decrease as the personnel retrieving the product from the containers are not working in unison, which leaves the burden of insuring that all product has been removed from each container on the last worker who must stop the conveyor to complete the removal of the remaining product in the containers. This disrupts activity further up the line. Usually, such starting and stopping occurs at frequent unpredictable intervals during operation.
Also, in other industries personnel are required to lift each item, crate or container from a stack (pallet) and manually place each crate one at a time on a conveyor or table for further processing. Such conventional manual item, crate or container destacking or depalletizing is time consuming and requires personnel to do heavy lifting.
Smith (U.S. Pat. No. 3,904,024) discloses an apparatus for assisting in the manual transferring of objects to or from a plurality of stacks of objects. The apparatus includes an elongate belt conveyor having means for moving the belt in either direction. The belt conveyor is pivotally supported at a first end about a vertical axis so that a second end can be moved in a horizontal, arcuate path from one stack of objects to another. The belt conveyor is also pivotally supported at the first end about a horizontal axis so that the second end can be moved in a vertical, arcuate path between a lower position in which the second end is located near the bottom of the stack and an upper position in which the second end is located near the top of the stack. A hydraulic lift is used to move the second end of the conveyor vertically. In the operation of the apparatus, objects are removed from stacks by having an operator stand on a platform of the hydraulic lift to one side of the second end of the conveyor. The operator has access to a control panel located along the side of the conveyor which enables the operator to control which direction the belt of the conveyor is driven and also to raise and lower the platform to place the second end of the conveyor adjacent the upper most layer of objects. The operator then manually transfers the objects from the uppermost layer onto the belt of the conveyor. When the stack is gone, the operator manually pushes the conveyor to the second stack and then manipulates the lift to move the conveyor back to the uppermost position and then manually starts removing objects from the second stack. When objects are to be moved onto the pallets (stacked), the above procedure is reversed.
Cornacchia (U.S. Pat. No. 5,108,255) discloses a palletizer and depalletizer having a pivotal clamp head and four pickup or deposit positions.
H. Grasvoll (U.S. Pat. No. 3,401,811) discloses a device for unloading pieces of goods from a pallet and transferring the goods to a conveyor. The device includes a lifting carriage adapted to lift and tilt a fully loaded pallet in a stepwise fashion to unload the pallet.
Rydell (U.S. Pat. No. 4,279,555) discloses a machine for stacking panels (palletizing) including an input conveyor for receiving the panels, an elevator conveyor pivotally connected to the discharge end of the input conveyor, a discharge conveyor at the outer end of the elevator conveyor, an elevator motor for moving the elevator conveyor about its pivot axis, and a switch on the discharge conveyor for activating the elevator motor as a panel is discharged therefrom to raise the elevator conveyor a selected distance prior to discharge of the next panel. The machine also includes a mechanism for controlling the length of the elevator conveyor to provide for a vertical stack.
McWilliams (U.S. Pat. No. 3,837,510) discloses a method and apparatus for loading bagged mail from a loading dock into a highway vehicle. A mailbag handling conveyor projects cantilever fashion from the forward end of a frame and is raised and lowered at its forward end by a swingably mounted leg that is movable between lowered and upright positions to vary the elevation of the discharging forward end of the conveyor.
Winski (U.S. Pat. No. 5,096,367) discloses a material handling apparatus and method for handling loose stacks of paper in pallets. The apparatus includes depalletizing, distributing and hopper loading apparatus, as well as material handling apparatus for transporting material therebetween.
Salsburg et al. (U.S. Pat. No. 5,487,638) discloses an apparatus and method for loading rolls of web into a chamber.
Hence, there is a need for an improved system and method for automatically destacking or depalletizing items, crates or containers.